U.S. patent application number 14/781157 was filed with the patent office on 2016-02-25 for dual threshold based cell clustering interference mitigation for eimta.
The applicant listed for this patent is Minghai FENG, Jilei HOU, QUALCOMM INCORPORATED, Neng WANG, Chao WEI. Invention is credited to Minghai Feng, Jilei Hou, Neng Wang, Chao Wei.
Application Number | 20160056907 14/781157 |
Document ID | / |
Family ID | 51866630 |
Filed Date | 2016-02-25 |
United States Patent
Application |
20160056907 |
Kind Code |
A1 |
Wei; Chao ; et al. |
February 25, 2016 |
DUAL THRESHOLD BASED CELL CLUSTERING INTERFERENCE MITIGATION FOR
eIMTA
Abstract
Methods, systems, and devices are described for interference
mitigation between neighboring cells through the use of cell
clusters and virtual logical cell clusters. Cells may be added to a
cell cluster with a first cell when a level of interference
coupling between the first cell and one or more neighboring cells
exceeds a first threshold. One or more other cells may be added to
a virtual logical cell cluster with the first cell when the level
of interference coupling is between a second threshold and the
first threshold, the second threshold being less than the first
threshold. Interference mitigation between cells of cell clusters
and/or virtual logical cell clusters may be performed. Interference
mitigation may be accomplished through, for example, coordination
of TDD uplink-downlink (UL-DL) configurations for cell clusters and
scheduling-dependent interference management (SDIM) for virtual
logical cell clusters.
Inventors: |
Wei; Chao; (Beijing, CN)
; Feng; Minghai; (Beijing, CN) ; Wang; Neng;
(Beijing, CN) ; Hou; Jilei; (Beijing, CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
WEI; Chao
FENG; Minghai
WANG; Neng
HOU; Jilei
QUALCOMM INCORPORATED |
San Diego |
CA |
US
US
US
US
US |
|
|
Family ID: |
51866630 |
Appl. No.: |
14/781157 |
Filed: |
May 8, 2014 |
PCT Filed: |
May 8, 2014 |
PCT NO: |
PCT/CN2014/077023 |
371 Date: |
September 29, 2015 |
Current U.S.
Class: |
370/280 |
Current CPC
Class: |
H04J 3/1694 20130101;
H04J 11/005 20130101; H04L 5/14 20130101; H04W 16/10 20130101; H04W
72/1226 20130101 |
International
Class: |
H04J 11/00 20060101
H04J011/00; H04L 5/14 20060101 H04L005/14; H04J 3/16 20060101
H04J003/16 |
Foreign Application Data
Date |
Code |
Application Number |
May 9, 2013 |
CN |
PCT/CN2013/075409 |
Claims
1. A method for wireless communication in a time division duplex
(TDD) communication system, comprising: identifying a plurality of
neighboring cells of a first cell; determining a level of
interference coupling between the first cell and each identified
neighboring cell; adding a first neighboring cell to a cell cluster
of the first cell when the level of interference coupling of the
first neighboring cell exceeds a first threshold; adding a second
neighboring cell to a virtual logical cell cluster when the level
of interference coupling of the second neighboring cell is between
a second threshold and the first threshold, the second threshold
being less than the first threshold; and performing interference
mitigation between the first cell and one or more cells in the
virtual logical cell cluster.
2. The method of claim 1, further comprising coordinating TDD
uplink-downlink (UL-DL) transmissions between the first cell and
one or more cells in the cell cluster.
3. The method of claim 2, wherein coordinating TDD UL-DL
transmissions comprises coordinating transmit directions of TDD
UL-DL subframes of the one or more cells in the cell cluster.
4. The method of claim 1, wherein performing interference
mitigation comprises applying one or more scheduling-dependent
interference management (SDIM) schemes.
5. The method of claim 4, wherein the one or more SDIM schemes
comprise one or more of uplink (UL) and downlink (DL) power
control.
6. The method of claim 2, wherein one or more TDD uplink-downlink
(UL-DL) subframes of the first cell and the second neighboring cell
have different transmit directions.
7. The method of claim 1, further comprising: changing a TDD
uplink-downlink (UL-DL) configuration of the cell cluster; and
transmitting an updated TDD UL-DL configuration to each cell in the
virtual logical cell cluster.
8. The method of claim 1, further comprising: receiving an updated
TDD uplink-downlink (UL-DL) configuration from a cell in the
virtual logical cell cluster; and changing the interference
mitigation responsive to the updated TDD UL-DL configuration.
9. The method of claim 1, further comprising: exchanging TDD
uplink-downlink (UL-DL) configuration information between the first
cell and each cell of the cell cluster; and exchanging TDD UL-DL
configuration information between the first cell and each cell of
the virtual logical cell cluster.
10. The method of claim 9, wherein the TDD UL-DL configuration
information is exchanged via an X2 interface coupled with the first
cell.
11. The method of claim 1, wherein a TDD uplink-downlink (UL-DL)
configuration of cells having interference coupling levels below
the second threshold may be modified independently of the
interference mitigation.
12. An apparatus for wireless communication in a time division
duplex (TDD) wireless communication system, comprising: means for
identifying a plurality of neighboring cells of a first cell; means
for determining a level of interference coupling between the first
cell and each identified neighboring cell; means for adding a first
neighboring cell to a cell cluster of the first cell when the level
of interference coupling of the first neighboring cell exceeds a
first threshold; means for adding a second neighboring cell to a
virtual logical cell cluster when the level of interference
coupling of the second neighboring cell is between a second
threshold and the first threshold, the second threshold being less
than the first threshold; and means for performing interference
mitigation between the first cell and one or more cells in the
virtual logical cell cluster.
13. The apparatus of claim 12, further comprising means for
coordinating TDD uplink-downlink (UL-DL) transmissions between the
first cell and one or more cells in the cell cluster.
14. The apparatus of claim 13, wherein the means for coordinating
TDD UL-DL transmissions comprises means for coordinating transmit
directions of TDD UL-DL subframes of the one or more cells in the
cell cluster.
15. The apparatus of claim 12, wherein the means for performing
interference mitigation comprises means for applying one or more
scheduling-dependent interference management (SDIM) schemes.
16. The apparatus of claim 15, wherein the one or more SDIM schemes
comprise one or more of uplink (UL) and downlink (DL) power
control.
17. The apparatus of claim 13, wherein one or more TDD
uplink-downlink (UL-DL) subframes of the first cell and the second
neighboring cell have different transmit directions.
18. The apparatus of claim 12, further comprising: means for
changing a TDD uplink-downlink (UL-DL) configuration of the cell
cluster; and means for transmitting an updated TDD UL-DL
configuration to each cell in the virtual logical cell cluster.
19. The apparatus of claim 12, further comprising: means for
receiving an updated TDD uplink-downlink (UL-DL) configuration from
a cell in the virtual logical cell cluster; and means for changing
the interference mitigation responsive to the updated TDD UL-DL
configuration.
20. The apparatus of claim 12, further comprising: means for
exchanging TDD uplink-downlink (UL-DL) configuration information
between the first cell and each cell of the cell cluster; and means
for exchanging TDD UL-DL configuration information between the
first cell and each cell of the virtual logical cell cluster.
21. The apparatus of claim 20, wherein the TDD UL-DL configuration
information is exchanged via an X2 interface coupled with the first
cell.
22. The apparatus of claim 12, wherein a TDD uplink-downlink
(UL-DL) configuration of cells having interference coupling levels
below the second threshold may be modified independently of the
interference mitigation.
23. An apparatus for wireless communication in a time division
duplex (TDD) wireless communication system, comprising: a
processor; memory in electronic communication with the processor;
and instructions being stored in the memory, the instructions being
executable by the processor to: identify a plurality of neighboring
cells of a first cell; determine a level of interference coupling
between the first cell and each identified neighboring cell; add a
first neighboring cell to a cell cluster of the first cell when the
level of interference coupling of the first neighboring cell
exceeds a first threshold; add a second neighboring cell to a
virtual logical cell cluster when the level of interference
coupling of the second neighboring cell is between a second
threshold and the first threshold, the second threshold being less
than the first threshold; and perform interference mitigation
between the first cell and one or more cells in the virtual logical
cell cluster.
24. The apparatus of claim 23, wherein the instructions are further
executable by the processor to: coordinate TDD uplink-downlink
(UL-DL) transmissions between the first cell and one or more cells
in the cell cluster.
25. The apparatus of claim 23, wherein the interference mitigation
comprises one or more scheduling-dependent interference management
(SDIM) schemes.
26. The apparatus of claim 25, wherein the one or more SDIM schemes
comprise one or more of uplink (UL) and downlink (DL) power
control.
27. The apparatus of claim 24, wherein one or more TDD
uplink-downlink (UL-DL) subframes of the first cell and the second
neighboring cell have different transmit directions.
28. The apparatus of claim 23, wherein the instructions are further
executable by the processor to: change a TDD uplink-downlink
(UL-DL) configuration of the cell cluster; and transmit an updated
TDD UL-DL configuration to each cell in the virtual logical cell
cluster.
29. The apparatus of claim 23, wherein the instructions are further
executable by the processor to: receive an updated TDD
uplink-downlink (UL-DL) configuration from a cell in the virtual
logical cell cluster; and change the interference mitigation
responsive to the updated TDD UL-DL configuration.
30. A computer program product for wireless communication in a time
division duplex (TDD) wireless communication system, the computer
program product comprising a non-transitory computer-readable
medium storing instructions executable by a processor to: identify
a plurality of neighboring cells of a first cell; determine a level
of interference coupling between the first cell and each identified
neighboring cell; add a first neighboring cell to a cell cluster of
the first cell when the level of interference coupling of the first
neighboring cell exceeds a first threshold; add a second
neighboring cell to a virtual logical cell cluster when the level
of interference coupling of the second neighboring cell is between
a second threshold and the first threshold, the second threshold
being less than the first threshold; and perform interference
mitigation between the first cell and one or more cells in the
virtual logical cell cluster.
Description
CROSS REFERENCES
[0001] The present application for patent claims priority to
International Patent Application No. PCT/CN2013/075409 to Qualcomm
Incorporated et al., entitled "Dual Threshold Based Cell Clustering
Interference Mitigation For eIMTA," filed May 9, 2013, assigned to
the assignee hereof, and expressly incorporated by reference
herein.
BACKGROUND
[0002] The following relates generally to wireless communication,
and more specifically to interference mitigation for neighboring
cells in a wireless communications system. Wireless communications
systems are widely deployed to provide various types of
communication content such as voice, video, packet data, messaging,
broadcast, and so on. These systems may be multiple-access systems
capable of supporting communication with multiple users by sharing
the available system resources (e.g., time, frequency, and power).
Examples of such multiple-access systems include code-division
multiple access (CDMA) systems, time-division multiple access
(TDMA) systems, frequency-division multiple access (FDMA) systems,
and orthogonal frequency-division multiple access (OFDMA) systems.
Additionally, some systems may operate using time-division duplex
(TDD), in which a single carrier frequency is used for both uplink
and downlink communications, and some systems may operate using
frequency-division duplex (FDD), in which separate carrier
frequencies are used for uplink and downlink communications.
[0003] In systems that operate using TDD, different formats may be
used in which uplink and downlink communications may be asymmetric.
TDD formats include transmission of frames of data, each including
a number of different subframes in which different subframes may be
uplink or downlink subframes. Reconfiguration of TDD formats may be
implemented in some systems based on data traffic patterns of the
particular system, in order to provide enhanced uplink or downlink
data capacity to users of the system.
SUMMARY
[0004] The described features generally relate to one or more
improved methods, systems, and/or apparatuses for wireless
communications in which interference between neighboring cells may
be mitigated through the use of cell clusters and virtual logical
cell clusters. Cells may be added to a cell cluster with a first
cell when a level of interference coupling between the first cell
and one or more neighboring cells exceeds a first threshold. One or
more other cells may be added to a virtual logical cell cluster
with the first cell when the level of interference coupling is
between a second threshold and the first threshold, the second
threshold being less than the first threshold. Interference
mitigation between cells of cell clusters and/or virtual logical
cell clusters may be performed. Interference mitigation may be
accomplished through, for example, coordination of TDD
uplink-downlink (UL-DL) configurations for cell clusters and
scheduling-dependent interference management (SDIM) for virtual
logical cell clusters.
[0005] In an aspect of the disclosure, a method for wireless
communication by a first cell operating according to time division
duplex (TDD) communication is provided. The method generally
includes identifying a plurality of neighboring cells of a first
cell, determining a level of interference coupling between the
first cell and each identified neighboring cell, adding a first
neighboring cell to a cell cluster of the first cell when the level
of interference coupling of the first neighboring cell exceeds a
first threshold, adding a second neighboring cell to a virtual
logical cell cluster when the level of interference coupling of the
second neighboring cell is between a second threshold and the first
threshold, the second threshold being less than the first
threshold, and performing interference mitigation between the first
cell and one or more cells in the virtual logical cell cluster. In
some examples, the method may further include coordinating TDD
uplink-downlink (UL-DL) transmissions between the first cell and
one or more cells in the cell cluster, such as through coordinating
transmit directions of TDD UL-DL subframes of the one or more cells
in the cell cluster, for example.
[0006] In some examples, performing interference mitigation may
include applying one or more scheduling-dependent interference
management (SDIM) schemes, such as, for example, one or more of UL
and DL power control. In some examples, one or more TDD UL-DL
subframes of the first cell and the second neighboring cell have
different transmit directions.
[0007] In some embodiments, the method may also include changing a
TDD UL-DL configuration of the cell cluster, and transmitting an
updated TDD UL-DL configuration to each cell in the virtual logical
cell cluster. Additionally or alternatively, the method may include
receiving an updated TDD UL-DL configuration from a cell in the
virtual logical cell cluster, and changing the interference
mitigation responsive to the updated TDD UL-DL configuration. In
further embodiments, the method may include exchanging TDD UL-DL
configuration information between the first cell and each cell of
the cell cluster, and exchanging TDD UL-DL configuration
information between the first cell and each cell of the virtual
logical cell cluster. The TDD UL-DL configuration information may
be exchanged, for example, via an X2 interface coupled with the
first cell. The TDD UL-DL configuration of cells having
interference coupling levels below the second threshold may be
modified independently of interference mitigation, according to
some embodiments.
[0008] In another aspect, the disclosure provides an apparatus for
wireless communication in a time division duplex (TDD) wireless
communication system. The apparatus generally includes means for
identifying a plurality of neighboring cells of a first cell, means
for determining a level of interference coupling between the first
cell and each identified neighboring cell, means for adding a first
neighboring cell to a cell cluster of the first cell when the level
of interference coupling of the first neighboring cell exceeds a
first threshold, means for adding a second neighboring cell to a
virtual logical cell cluster when the level of interference
coupling of the second neighboring cell is between a second
threshold and the first threshold, the second threshold being less
than the first threshold, and means for performing interference
mitigation between the first cell and one or more cells in the
virtual logical cell cluster.
[0009] The apparatus may also include, in some embodiments, means
for coordinating TDD uplink-downlink (UL-DL) transmissions between
the first cell and one or more cells in the cell cluster. The means
for coordinating TDD UL-DL transmissions may include, for example,
means for coordinating transmit directions of TDD UL-DL subframes
of the one or more cells in the cell cluster.
[0010] In some embodiments, the means for performing interference
mitigation comprises means for applying one or more
scheduling-dependent interference management (SDIM) schemes. The
one or more SDIM schemes may include, for example, one or more of
UL and DL power control. In some embodiments, the one or more TDD
UL-DL subframes of the first cell and the second neighboring cell
have different transmit directions.
[0011] The apparatus, in some embodiments, may further include
means for changing a TDD UL-DL configuration of the cell cluster,
and means for transmitting an updated TDD UL-DL configuration to
each cell in the virtual logical cell cluster. Additionally or
alternatively, the apparatus may include means for receiving an
updated TDD UL-DL configuration from a cell in the virtual logical
cell cluster, and means for changing the interference mitigation
responsive to the updated TDD UL-DL configuration. The apparatus
may also include, in some embodiments, means for exchanging TDD
UL-DL configuration information between the first cell and each
cell of the cell cluster, and means for exchanging TDD UL-DL
configuration information between the first cell and each cell of
the virtual logical cell cluster. The means for exchanging may be,
for example, an X2 interface coupled with the first cell. The TDD
UL-DL configuration of cells having interference coupling levels
below the second threshold may be modified independently of
interference mitigation, according to some embodiments.
[0012] In another aspect, the disclosure provides another apparatus
for wireless communication in a time division duplex (TDD) wireless
communication system. The apparatus generally includes a processor,
memory in electronic communication with the processor, and
instructions being stored in the memory. The instructions may be
executable by the processor to identify a plurality of neighboring
cells of a first cell, determine a level of interference coupling
between the first cell and each identified neighboring cell, add a
first neighboring cell to a cell cluster of the first cell when the
level of interference coupling of the first neighboring cell
exceeds a first threshold, add a second neighboring cell to a
virtual logical cell cluster when the level of interference
coupling of the second neighboring cell is between a second
threshold and the first threshold, the second threshold being less
than the first threshold, and perform interference mitigation
between the first cell and one or more cells in the virtual logical
cell cluster.
[0013] In some embodiments, the instructions may be further
executable by the processor to coordinate TDD uplink-downlink
(UL-DL) transmissions between the first cell and one or more cells
in the cell cluster. The coordination of TDD UL-DL transmissions
may include, for example, coordinating transmit directions of TDD
UL-DL subframes of the one or more cells in the cell cluster. The
interference mitigation may include, in some embodiments, one or
more scheduling-dependent interference management (SDIM) schemes,
such as one or more of UL and DL power control.
[0014] In some embodiments, the instructions may be further
executable by the processor to change a TDD UL-DL configuration of
the cell cluster, and transmit an updated TDD UL-DL configuration
to each cell in the virtual logical cell cluster. Additionally or
alternatively, the instructions may be further executable by the
processor to receive an updated TDD UL-DL configuration from a cell
in the virtual logical cell cluster, and change the interference
mitigation responsive to the updated TDD UL-DL configuration. In
some embodiments, the instructions may be further executable by the
processor to exchange TDD UL-DL configuration information between
the first cell and each cell of the cell cluster, and exchange TDD
UL-DL configuration information between the first cell and each
cell of the virtual logical cell cluster.
[0015] In another aspect, the disclosure provides a computer
program product for wireless communication in a time division
duplex (TDD) wireless communication system. The computer program
product generally includes a non-transitory computer-readable
medium storing instructions executable by a processor. The
instructions may be executable by the processor to identify a
plurality of neighboring cells of a first cell, determine a level
of interference coupling between the first cell and each identified
neighboring cell, add a first neighboring cell to a cell cluster of
the first cell when the level of interference coupling of the first
neighboring cell exceeds a first threshold, add a second
neighboring cell to a virtual logical cell cluster when the level
of interference coupling of the second neighboring cell is between
a second threshold and the first threshold, the second threshold
being less than the first threshold, and perform interference
mitigation between the first cell and one or more cells in the
virtual logical cell cluster.
[0016] In some embodiments, the instructions may be further
executable by the processor to coordinate TDD uplink-downlink
(UL-DL) transmissions between the first cell and one or more cells
in the cell cluster. The coordination of TDD UL-DL transmissions
may include, for example, coordinating transmit directions of TDD
UL-DL subframes of the one or more cells in the cell cluster. The
interference mitigation may include, for example, one or more
scheduling-dependent interference management (SDIM) schemes, such
as one or more of UL and DL power control.
[0017] In some embodiments, the instructions may be further
executable by the processor to change a TDD UL-DL configuration of
the cell cluster, and transmit an updated TDD UL-DL configuration
to each cell in the virtual logical cell cluster. Additionally or
alternatively, the instructions may be further executable by the
processor to receive an updated TDD UL-DL configuration from a cell
in the virtual logical cell cluster, and change the interference
mitigation responsive to the updated TDD UL-DL configuration. The
instructions, in some embodiments, may be further executable by the
processor to exchange TDD UL-DL configuration information between
the first cell and each cell of the cell cluster, and exchange TDD
UL-DL configuration information between the first cell and each
cell of the virtual logical cell cluster.
[0018] In another aspect, the disclosure provides another method
for wireless communication in a time division duplex (TDD)
communication system. The method generally includes identifying a
first interference coupling threshold above which a first cell and
a neighboring cell are assigned to a same cell cluster, identifying
a range of interference coupling levels between a second
interference coupling threshold and the first interference coupling
threshold for assigning the first cell and the neighboring cell to
a virtual logical cell cluster for interference mitigation, and
determining whether the first cell and the neighboring cell are to
be part of a same cell cluster or a virtual logical cell cluster
based on a level of interference coupling between the first cell
and the neighboring cell. Cells within a same cell cluster may, for
example, coordinate TDD uplink-downlink (UL-DL) transmissions.
Interference mitigation for cells in the virtual logical cell
cluster may include, for example, applying one or more
scheduling-dependent interference management (SDIM) schemes, such
as UL and/or DL power control. The TDD UL-DL configuration of cells
having interference coupling levels below the second threshold may,
in some embodiments, be modified independently of interference
mitigation.
[0019] In a further aspect, an apparatus for wireless communication
in a time division duplex (TDD) communication system is provided.
The apparatus generally includes means for identifying a first
interference coupling threshold above which a first cell and a
neighboring cell are assigned to a same cell cluster, means for
identifying a range of interference coupling levels between a
second interference coupling threshold and the first interference
coupling threshold for assigning the first cell and the neighboring
cell to a virtual logical cell cluster for interference mitigation,
and means for determining whether the first cell and the
neighboring cell are to be part of a same cell cluster or a virtual
logical cell cluster based on a level of interference coupling
between the first cell and the neighboring cell. Cells within a
same cell cluster may, for example, coordinate TDD uplink-downlink
(UL-DL) transmissions. The means for performing interference
mitigation for cells in the virtual logical cell cluster may
include, for example, means for applying one or more
scheduling-dependent interference management (SDIM) schemes, such
as UL and/or DL power control. The TDD UL-DL configuration of cells
having interference coupling levels below the second threshold may,
in some embodiments, be modified independently of interference
mitigation.
[0020] In a further aspect, the disclosure provides an apparatus
for wireless communication in a time division duplex (TDD) wireless
communication system. The apparatus generally includes a processor,
memory in electronic communication with the processor, and
instructions being stored in the memory. The instructions may be
executable by the processor to identify a first interference
coupling threshold above which a first cell and a neighboring cell
are assigned to a same cell cluster, identify a range of
interference coupling levels between a second interference coupling
threshold and the first interference coupling threshold for
assigning the first cell and the neighboring cell to a virtual
logical cell cluster for interference mitigation, and determine
whether the first cell and the neighboring cell are to be part of a
same cell cluster or a virtual logical cell cluster based on a
level of interference coupling between the first cell and the
neighboring cell. Cells within a same cell cluster may, in some
examples, coordinate TDD uplink-downlink (UL-DL) transmissions.
Interference mitigation for cells in the virtual logical cell
cluster may include, for example, one or more scheduling-dependent
interference management (SDIM) schemes.
[0021] In still a further aspect, the disclosure provides a
computer program product for wireless communication in a time
division duplex (TDD) wireless communication system. The computer
program product includes a non-transitory computer-readable medium
storing instructions executable by a processor. The instructions
may be executable by the processor to identify a first interference
coupling threshold above which a first cell and a neighboring cell
are assigned to a same cell cluster, identify a range of
interference coupling levels between a second interference coupling
threshold and the first interference coupling threshold for
assigning the first cell and the neighboring cell to a virtual
logical cell cluster for interference mitigation, and determine
whether the first cell and the neighboring cell are to be part of a
same cell cluster or a virtual logical cell cluster based on a
level of interference coupling between the first cell and the
neighboring cell. Cells within a same cell cluster may, for
example, coordinate TDD uplink-downlink (UL-DL) transmissions.
Interference mitigation for cells in the virtual logical cell
cluster may include, for example, one or more scheduling-dependent
interference management (SDIM) schemes.
[0022] Further scope of the applicability of the described methods
and apparatuses will become apparent from the following detailed
description, claims, and drawings. The detailed description and
specific examples are given by way of illustration only, since
various changes and modifications within the spirit and scope of
the description will become apparent to those skilled in the
art.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] A further understanding of the nature and advantages of the
present invention may be realized by reference to the following
drawings. In the appended figures, similar components or features
may have the same reference label. Further, various components of
the same type may be distinguished by following the reference label
by a dash and a second label that distinguishes among the similar
components. If only the first reference label is used in the
specification, the description is applicable to any one of the
similar components having the same first reference label
irrespective of the second reference label.
[0024] FIG. 1 is a diagram illustrating an example of a wireless
communications system in accordance with various embodiments;
[0025] FIG. 2 is a table illustrating TDD Uplink-Downlink
configurations in a wireless communications system in accordance
with various embodiments;
[0026] FIG. 3 illustrates a Cell Clustering Interference Mitigation
environment with cells grouped according to cell clusters in
accordance with various embodiments;
[0027] FIG. 4 illustrates cell clusters and virtual logical cell
clusters in accordance with various embodiments;
[0028] FIG. 5 illustrates different thresholds of interference
level coupling levels for a base station;
[0029] FIG. 6 shows a block diagram of an example of a base station
in accordance with various embodiments;
[0030] FIG. 7 shows a block diagram of an example of a user
equipment in accordance with various embodiments;
[0031] FIG. 8 shows a block diagram of an example of a user
equipment and base station in accordance with various
embodiments;
[0032] FIG. 9 is a flowchart of a method for interference
mitigation in accordance with various embodiments;
[0033] FIG. 10 is a flowchart of another method for interference
mitigation in accordance with various embodiments;
[0034] FIG. 11 is a flowchart of yet another method for
interference mitigation in accordance with various embodiments;
and
[0035] FIG. 12 is a flowchart of still another method for
interference mitigation in accordance with various embodiments.
DETAILED DESCRIPTION
[0036] Various aspects of the disclosure provide for wireless
communications in which interference between neighboring cells may
be mitigated through the use of cell clusters and virtual logical
cell clusters. Cells may be added to a cell cluster with a first
cell when a level of interference coupling between the first cell
and one or more neighboring cells exceeds a first threshold. One or
more other cells may be added to a virtual logical cell cluster
with the first cell when the level of interference coupling is
between a second threshold and the first threshold, the second
threshold being less than the first threshold. Interference
mitigation between cells of cell clusters and/or virtual logical
cell clusters may be performed. Interference mitigation may be
accomplished through, for example, coordination of TDD
uplink-downlink (UL-DL) configurations for cell clusters and
scheduling-dependent interference management (SDIM) for virtual
logical cell clusters.
[0037] Techniques described herein may be used for various wireless
communications systems such as cellular wireless systems,
Peer-to-Peer wireless communications, wireless local access
networks (WLANs), ad hoc networks, satellite communications
systems, and other systems. The terms "system" and "network" are
often used interchangeably. These wireless communications systems
may employ a variety of radio communication technologies such as
Code Division Multiple Access (CDMA), Time Division Multiple Access
(TDMA), Frequency Division Multiple Access (FDMA), Orthogonal FDMA
(OFDMA), Single-Carrier FDMA (SC-FDMA), and/or other radio
technologies. Generally, wireless communications are conducted
according to a standardized implementation of one or more radio
communication technologies called a Radio Access Technology (RAT).
A wireless communications system or network that implements a Radio
Access Technology may be called a Radio Access Network (RAN).
[0038] Examples of Radio Access Technologies employing CDMA
techniques include CDMA2000, Universal Terrestrial Radio Access
(UTRA), etc. CDMA2000 covers IS-2000, IS-95, and IS-856 standards.
IS-2000 Releases 0 and A are commonly referred to as CDMA2000
1.times., 1.times., etc. IS-856 (TIA-856) is commonly referred to
as CDMA2000 1.times.EV-DO, High Rate Packet Data (HRPD), etc. UTRA
includes Wideband CDMA (WCDMA) and other variants of CDMA. Examples
of TDMA systems include various implementations of Global System
for Mobile Communications (GSM). Examples of Radio Access
Technologies employing OFDM and/or OFDMA include Ultra Mobile
Broadband (UMB), Evolved UTRA (E-UTRA), IEEE 802.11 (Wi-Fi), IEEE
802.16 (WiMAX), IEEE 802.20, Flash-OFDM, etc. UTRA and E-UTRA are
part of Universal Mobile Telecommunication System (UMTS). 3GPP Long
Term Evolution (LTE) and LTE-Advanced (LTE-A) are new releases of
UMTS that use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A, and GSM are
described in documents from an organization named "3rd Generation
Partnership Project" (3GPP). CDMA2000 and UMB are described in
documents from an organization named "3rd Generation Partnership
Project 2" (3GPP2). The techniques described herein may be used for
the systems and radio technologies mentioned above as well as other
systems and radio technologies.
[0039] Thus, the following description provides examples, and is
not limiting of the scope, applicability, or configuration set
forth in the claims. Changes may be made in the function and
arrangement of elements discussed without departing from the spirit
and scope of the disclosure. Various embodiments may omit,
substitute, or add various procedures or components as appropriate.
For instance, the methods described may be performed in an order
different from that described, and various steps may be added,
omitted, or combined. Also, features described with respect to
certain embodiments may be combined in other embodiments.
[0040] Referring first to FIG. 1, a diagram illustrates an example
of a wireless communications system 100. The system 100 includes
base stations (or cells) 105, user equipments (UEs) 115, and a core
network 130. The base stations 105 may communicate with the UEs 115
under the control of a base station controller (not shown), which
may be part of the core network 130 or the base stations 105 in
various embodiments. Base stations 105 may communicate control
information and/or user data with the core network 130 through
backhaul links 132. Backhaul links may be wired backhaul links
(e.g., copper, fiber, etc.) and/or wireless backhaul links (e.g.,
microwave, etc.). In embodiments, the base stations 105 may
communicate, either directly or indirectly, with each other over
backhaul links 134, which may be wired or wireless communication
links. The system 100 may support operation on multiple carriers
(waveform signals of different frequencies). Multi-carrier
transmitters can transmit modulated signals simultaneously on the
multiple carriers. For example, each communication link 125 may be
a multi-carrier signal modulated according to the various radio
technologies described above. Each modulated signal may be sent on
a different carrier and may carry control information (e.g.,
reference signals, control channels, etc.), overhead information,
data, etc.
[0041] The base stations 105 may wirelessly communicate with the
UEs 115 via one or more base station antennas. Each of the base
station 105 sites may provide communication coverage for a
respective geographic coverage area 110. In some embodiments, base
stations 105 may be referred to as a base transceiver station, a
radio base station, an access point, a radio transceiver, a basic
service set (BSS), an extended service set (ESS), a NodeB, eNodeB
(eNB), Home NodeB, a Home eNodeB, or some other suitable
terminology. The coverage area 110 for a base station may be
divided into sectors making up only a portion of the coverage area
(not shown). The system 100 may include base stations 105 of
different types (e.g., macro, micro, and/or pico base stations).
There may be overlapping coverage areas for different technologies.
According to various embodiments, base stations may be assigned to
clusters for purposes of interference mitigation. For example,
neighboring base stations having relatively high levels of
interference coupling may belong to a cell cluster in which
communications of the base stations are coordinated (e.g.,
receive/transmit uplink/downlink communications in a coordinated
fashion), and neighboring base stations having moderate levels of
interference coupling may employ interference management techniques
(e.g., SDIM). Various examples of interference mitigation will be
described in further detail below.
[0042] The wireless communications system 100 may support
synchronous or asynchronous operation. For synchronous operation,
the eNBs may have similar frame timing, and transmissions from
different eNBs may be approximately aligned in time. For
asynchronous operation, the eNBs may have different frame timing,
and transmissions from different eNBs may not be aligned in time.
In embodiments, some eNBs 105 may be synchronous while other eNBs
may be asynchronous.
[0043] The UEs 115 are dispersed throughout the wireless
communications system 100, and each device may be stationary or
mobile. A UE 115 may also be referred to by those skilled in the
art as a mobile station, a subscriber station, a mobile unit, a
subscriber unit, a wireless unit, a remote unit, a mobile device, a
wireless device, a wireless communications device, a remote device,
a mobile subscriber station, an access terminal, a mobile terminal,
a wireless terminal, a remote terminal, a handset, a user agent, a
user equipment, a mobile client, a client, or some other suitable
terminology. A UE 115 may be a cellular phone, a personal digital
assistant (PDA), a wireless modem, a wireless communication device,
a handheld device, a tablet computer, a laptop computer, a cordless
phone, a wireless local loop (WLL) station, or the like. A
communication device may be able to communicate with macro base
stations, pico base stations, femto base stations, relay base
stations, and the like.
[0044] The communication links 125 shown in the wireless
communications system 100 may include uplink (UL) transmissions
from a UE 115 to a base station 105, and/or downlink (DL)
transmissions, from a base station 105 to a UE 115. The downlink
transmissions may also be called forward link transmissions while
the uplink transmissions may also be called reverse link
transmissions. In embodiments, the communication links 125 are TDD
carriers carrying bidirectional traffic within traffic frames.
[0045] In embodiments, the system 100 is an LTE/LTE-A network. In
LTE/LTE-A networks, the term evolved Node B (eNB) may be generally
used to describe the base stations 105 and UEs 115, respectively.
The system 100 may be a Heterogeneous LTE/LTE-A network in which
different types of eNBs provide coverage for various geographical
regions. For example, each eNB 105 may provide communication
coverage for a macro cell, a pico cell, a femto cell, and/or other
types of cell. A macro cell generally covers a relatively large
geographic area (e.g., several kilometers in radius) and may allow
unrestricted access by UEs with service subscriptions with the
network provider. A pico cell would generally cover a relatively
smaller geographic area and may allow unrestricted access by UEs
with service subscriptions with the network provider. A femto cell
would also generally cover a relatively small geographic area
(e.g., a home) and, in addition to unrestricted access, may also
provide restricted access by UEs having an association with the
femto cell (e.g., UEs in a closed subscriber group (CSG), UEs for
users in the home, and the like). An eNB for a macro cell may be
referred to as a macro eNB. An eNB for a pico cell may be referred
to as a pico eNB. And, an eNB for a femto cell may be referred to
as a femto eNB or a home eNB. An eNB may support one or multiple
(e.g., two, three, four, and the like) cells.
[0046] The wireless communications system 100 according to an
LTE/LTE-A network architecture may be referred to as an Evolved
Packet System (EPS). The EPS may include one or more UEs 115, an
Evolved UMTS Terrestrial Radio Access Network (E-UTRAN), an Evolved
Packet Core (EPC) (e.g., core network 130), a Home Subscriber
Server (HSS), and an Operator's IP Services. The EPS may
interconnect with other access networks using other Radio Access
Technologies. For example, the EPS may interconnect with a
UTRAN-based network and/or a CDMA-based network via one or more
Serving GPRS Support Nodes (SGSNs). To support mobility of UEs 115
and/or load balancing, the EPS may support handover of UEs 115
between a source eNB 105 and a target eNB 105. The EPS may support
intra-RAT handover between eNBs 105 and/or base stations of the
same RAT (e.g., other E-UTRAN networks), and inter-RAT handovers
between eNBs and/or base stations of different RATs (e.g., E-UTRAN
to CDMA, etc.). The EPS may provide packet-switched services,
however, as those skilled in the art will readily appreciate, the
various concepts presented throughout this disclosure may be
extended to networks providing circuit-switched services.
[0047] The E-UTRAN may include the eNBs 105 and may provide user
plane and control plane protocol terminations toward the UEs 115.
The eNBs 105 may be connected to other eNBs 105 via an X2 interface
(e.g., backhaul link 134). The eNBs 105 may provide an access point
to the core network (e.g., the EPC) for the UEs 115. The eNBs 105
may be connected by an S1 interface (e.g., backhaul link 132) to
the core network 130 (e.g., the EPC). Logical nodes within the core
network 130 or EPC may include one or more Mobility Management
Entities (MMEs), one or more Serving Gateways, and one or more
Packet Data Network (PDN) Gateways (not shown). Generally, the MME
may provide bearer and connection management. All user IP packets
may be transferred through the Serving Gateway, which itself may be
connected to the PDN Gateway. The PDN Gateway may provide UE IP
address allocation as well as other functions. The PDN Gateway may
be connected to IP networks and/or the operator's IP Services.
These logical nodes may be implemented in separate physical nodes
or one or more may be combined in a single physical node. The IP
Networks/Operator's IP Services may include the Internet, an
Intranet, an IP Multimedia Subsystem (IMS), and/or a
Packet-Switched (PS) Streaming Service (PSS).
[0048] The UEs 115 may be configured to collaboratively communicate
with multiple eNBs 105 through, for example, Multiple Input
Multiple Output (MIMO), Coordinated Multi-Point (CoMP), or other
schemes. MIMO techniques use multiple antennas on the base stations
and/or multiple antennas on the UE to take advantage of multipath
environments to transmit multiple data streams. CoMP includes
techniques for dynamic coordination of transmission and reception
by a number of eNBs to improve overall transmission quality for UEs
as well as increasing network and spectrum utilization. Generally,
CoMP techniques utilize backhaul links 132 and/or 134 for
communication between base stations 105 to coordinate control plane
and user plane communications for the UEs 115.
[0049] The communication networks that may accommodate some of the
various disclosed embodiments may be packet-based networks that
operate according to a layered protocol stack. In the user plane,
communications at the bearer or Packet Data Convergence Protocol
(PDCP) layer may be IP-based. A Radio Link Control (RLC) layer may
perform packet segmentation and reassembly to communicate over
logical channels. A Medium Access Control (MAC) layer may perform
priority handling and multiplexing of logical channels into
transport channels. The MAC layer may also use Hybrid ARQ (HARQ) to
provide retransmission at the MAC layer to improve link efficiency.
In the control plane, the Radio Resource Control (RRC) protocol
layer may provide establishment, configuration, and maintenance of
an RRC connection between the UE and the network used for the user
plane data. At the Physical layer, the transport channels may be
mapped to Physical channels.
[0050] LTE/LTE-A utilizes orthogonal frequency division
multiple-access (OFDMA) on the downlink and single-carrier
frequency division multiple-access (SC-FDMA) on the uplink. OFDMA
and SC-FDMA partition the system bandwidth into multiple (K)
orthogonal subcarriers, which are also commonly referred to as
tones, bins, or the like. Each subcarrier may be modulated with
data. The spacing between adjacent subcarriers may be fixed, and
the total number of subcarriers (K) may be dependent on the system
bandwidth. For example, K may be equal to 72, 180, 300, 600, 900,
or 1200 with a subcarrier spacing of 15 kilohertz (KHz) for a
corresponding system bandwidth (with guardband) of 1.4, 3, 5, 10,
15, or 20 megahertz (MHz), respectively. The system bandwidth may
also be partitioned into sub-bands. For example, a sub-band may
cover 1.08 MHz, and there may be 1, 2, 4, 8 or 16 sub-bands.
[0051] Wireless communications system 100 may support operation on
multiple carriers, which may be referred to as carrier aggregation
(CA) or multi-carrier operation. A carrier may also be referred to
as a component carrier (CC), a channel, etc. The terms "carrier,"
"CC," and "channel" may be used interchangeably herein. A carrier
used for the downlink may be referred to as a downlink CC, and a
carrier used for the uplink may be referred to as an uplink CC. A
UE may be configured with multiple downlink CCs and one or more
uplink CCs for carrier aggregation. An eNB may transmit data and
control information on one or more downlink CCs to the UE. The UE
may transmit data and control information on one or more uplink CCs
to the eNB.
[0052] The carriers may transmit bidirectional communications FDD
(e.g., paired spectrum resources), TDD (e.g., unpaired spectrum
resources). Frame structures for FDD (e.g., frame structure type 1)
and TDD (e.g., frame structure type 2) may be defined. Each frame
structure may have a radio frame length T.sub.f=307200T.sub.s=10 ms
and may include two half-frames of length 153600T.sub.s=5 ms each.
Each half-frame may include five subframes of length 30720T.sub.s=1
ms.
[0053] For TDD frame structures, each subframe may carry UL or DL
traffic, and special subframes ("S") may be used to switch between
DL to UL transmission. Allocation of UL and DL subframes within
radio frames may be symmetric or asymmetric and may be reconfigured
semi-statically (e.g., RRC messages via backhaul, etc.). Special
subframes may carry some DL and/or UL traffic and may include a
Guard Period (GP) between DL and UL traffic. Switching from UL to
DL traffic may be achieved by setting timing advance at the UEs
without the use of Special subframes or a guard period between UL
and DL subframes. UL-DL configurations with switch-point
periodicity equal to the frame period (e.g., 10 ms) or half of the
frame period (e.g., 5 ms) may be supported. For example, TDD frames
may include one or more Special frames, and the period between
Special frames may determine the TDD DL-to-UL switch-point
periodicity for the frame. For LTE/LTE-A, seven different UL-DL
configurations are defined that provide between 40% and 90% DL
subframes as illustrated in table FIG. 2 at Table 200. As indicated
in table 200, there are two switching periodicities, 5 ms and 10
ms. For configurations with 5 ms switching periodicities, there are
two special subframes per frame, and for configurations with 10 ms
switching periodicities there is one special subframe per frame.
Some of these configurations are symmetric, having the same number
of uplink and downlink subframes, while some are asymmetric, having
different numbers of uplink and downlink subframes. For example,
UL-DL configuration 1 is symmetric, with four uplink and four
downlink subframes, UL-DL configuration 5 favors downlink
throughput, and UL-DL configuration 0 favors uplink throughput.
[0054] The particular TDD UL/DL configuration that is used by a
base station may be based on user requirements for the particular
coverage area. For example, with reference again to FIG. 1, if a
relatively large number of users in a coverage area 110 are
receiving more data than they are transmitting, the UL-DL
configuration for the associated base station 105 may be selected
to favor downlink throughput. Similarly, if a relatively large
number of users in a coverage are 110 are transmitting more data
than they are receiving, the UL-DL configuration for the associated
base station 105 may be selected to favor uplink throughput and the
base station 105 may operate using UL-DL configuration 0. In some
aspects, a base station 105 may be able to dynamically reconfigure
TDD UL-DL configurations on a frame-by-frame basis. For example, in
some versions of LTE specifications, it is possible to dynamically
adapt TDD DL-UL subframe configurations based on the actual traffic
needs, also referred to as evolved Interference Management for
Traffic Adaptation (eIMTA). If, during a short duration, a large
data burst on downlink is needed, the configuration can be changed
from, for example, configuration #1 (6 DL, 4 UL) to configuration
#5 (9 DL:1 UL). The adaptation of TDD configuration, in some cases,
may be no slower than 640 ms, and in some cases may be as fast as
10 ms. The adaptation, however, may cause significant interference
to both downlink and uplink when, for example, two or more
neighboring cells have different downlink and uplink subframes. For
example, a first cell may be operating in TDD UL-DL configuration
#1 (D S U U D D S U U D), and if a neighboring cell were to be
operating in TDD UL-DL configuration #3 (D S U U U D D D D D), in
the same subframe, an uplink transmission for the first cell may
cause interference with a downlink reception for the neighboring
cell. According to various embodiments, cells may be assigned to a
cell cluster or a virtual logical cell cluster according to a level
of interference coupling between base stations, as will be
described in more detail below.
[0055] FIG. 3 illustrates a Cell Clustering and Interference
Mitigation (CCIM) environment 300 with eNBs grouped according to
cell clusters. CCIM environment 300 may illustrate, for example,
aspects of wireless communications system 100 illustrated in FIG.
1. Cell clusters can include one or more eNBs and eNBs within a
cell cluster may be different types (e.g., macro eNB, pico eNB,
femto eNB, and/or the like). As illustrated in the example of FIG.
3, CCIM environment 300 includes cell clusters 305-a, 305-b, and
305-c. Cell cluster 305-a may include eNB 105-a and eNB 105-b, cell
cluster 305-b may include eNB 105-c, and cell cluster 305-c may
include eNBs 105-d and 105-e. Cell clusters 305 may be statically
or semi-statically defined and each eNB 105 in a cell cluster 305
may be aware of the other eNBs 105 of its cluster. Cell clusters
305-a, 305-b, and/or 305-c may deploy TDD carriers and TDD UL-DL
configuration within each cell cluster may be synchronized.
[0056] Traffic adaptation for synchronized TDD UL-DL configuration
within a cell cluster may be performed by coordination of TDD UL-DL
reconfiguration between cells of the cluster. Semi-static (e.g., on
the order of tens of frames) TDD UL-DL reconfiguration may be
performed by exchange of control-plane messaging among eNBs (e.g.,
via S1 and/or X2 interfaces, etc.). While semi-static TDD UL-DL
reconfiguration may provide adequate performance under some
conditions, when traffic conditions within the cluster change
rapidly, semi-static TDD UL-DL reconfiguration may result in
sub-optimal allocation of UL-to-DL subframes for TDD carriers used
in the cluster. In some aspects, rapidly changing traffic
conditions may be accommodated through allowing the UL-DL
configuration for a particular UE 115 may be reconfigured
dynamically. Such dynamic reconfiguration may be transmitted to a
UE 115 through signaling from the eNB 105, such as through control
channel signaling or other techniques, and apply to one or more
subsequent TDD frames. Such reconfigurations may be accomplished
according to eIMTA, which, as mentioned above, may be implemented
in some networks.
[0057] As noted above, depending upon the configuration of cells,
inter-cell interference may occur. For example, with continued
reference to FIG. 3, cell cluster 305-c could, in some scenarios,
include eNB 105-d operating according to TDD UL-DL configuration
one (having subframe configuration DSUUDDSUUD) and eNB 105-e
operating according to TDD UL-DL configuration three (having
subframe configuration DSUUUDDDDD). In such a case, uplink
transmissions for eNB 105-d in subframes 6, 7 and 8 may interfere
with a downlink reception of UEs in communication with eNB 105-e.
Thus, according to various embodiments, eNBs 105-d and 105-e may
coordinate to reduce the likelihood of such interference.
Interference may include, for example, eNB-to-eNB interference,
indicated at 310-a, 310-b, and 310-c. Interference may also
include, for example, UE-to-UE interference indicated at 315-a and
315-b. According to various embodiments, eNBs 105 may be assigned
to a cell cluster 305 and one or more virtual logical cell
clusters, as will be described in more detail below, based on an
interference level between neighboring cells. When operating
according to dynamically reconfigurable TDD UL-DL configurations,
according to various embodiments, signaling to indicate the TDD
UL-DL configuration of a cell may be provided to other cells in a
cluster and one or more virtual logical cell clusters, and eNBs of
the cluster and virtual logical cell cluster(s) may perform various
interference mitigation techniques responsive to the TDD UL-DL
configuration. Methods of signaling TDD configuration may include,
for example signaling over the S1 and/or X2 interface link
[0058] With reference now to FIG. 4, illustrates a Cell Clustering
and Interference Mitigation (CCIM) environment 400 with eNBs
grouped according to cell clusters and virtual logical cell
clusters in accordance with various embodiments. CCIM environment
400 may illustrate, for example, aspects of wireless communications
system 100 illustrated in FIG. 1 and/or the CCIM environment 300
illustrated in FIG. 3. Similarly as with FIG. 3, cell clusters can
include one or more eNBs and eNBs within a cell cluster may be
different types (e.g., macro eNB, pico eNB, femto eNB, and/or the
like). As illustrated in the example of FIG. 4, CCIM environment
400 includes cell clusters 405-a, 405-b, and 405-c. Cell cluster
405-a may include eNB 105-f and eNB 105-g, cell cluster 405-b may
include eNB 105-h, and cell cluster 405-c may include eNBs 105-i
and 105-j. Cell clusters 405 may be statically or semi-statically
defined and each eNB 105 in a cell cluster 405 may be aware of the
other eNBs 105 of its cluster. Cell clusters 405-a, 405-b, and/or
405-c may deploy TDD carriers and TDD UL-DL configuration within
each cell cluster may be synchronized.
[0059] As discussed above, TDD reconfiguration, such as may be
employed in eIMTA for example, may result in interference between
eNBs 105. According to various aspects, the level of interference
coupling between eNBs may be determined, and two or more
neighboring eNBs may be assigned to a cell cluster 405 if
interference coupling is greater than a first threshold. In some
examples, a coupling loss may be determined between an eNB 105 and
each of a number of neighboring eNBs. The coupling loss, which may
be correlated to an interference coupling level between eNBs 105,
may be used as an indication of the amount of interference that may
be present for transmissions from the eNBs 105. According to some
embodiments, eNBs 105 that have coupling loss greater than a
threshold are combined into cell clusters 405, and each cluster
applies coordinated adaptation of UL-DL configuration taking into
account aggregated traffic within the cluster. For example, by
setting a coupling threshold (e.g. -90 dB in case of outdoor
picocells only) which determines cells in a cluster (and thus
coordinated TDD UL-DL configurations), the UL SINR when applying
TDD eIMTA may in some cases be improved to a level very close to
the case with fixed UL-DL configurations. However, such cell
clustering may reduce traffic adaptation flexibility, because all
the cells in one cluster are configured with same UL-DL
configuration. Thus, if one particular eNB 105 would benefit from a
chanced TDD UL-DL configuration, such a change may not in some
instances be able to be made. For example, some implementations may
employ 4 pico cells per Macro cell, which may result in about 36%
of cells belonging to clusters with three or more cells. In
deployments using dense pico-cell deployment (e.g. 8 pico cells per
Macro cell), only 13% of cells are isolated cells. Thus, cell
clustering techniques may limit the flexibility for an eNB 105 to
reconfigure its TDD UL-DL configuration.
[0060] According to some implementations, a relatively high
threshold of coupling loss, such as -70 dB coupling loss instead of
-90 dB for example, may be selected to reduce cluster size and
increase adaptation flexibility. Such implementations may result in
neighboring cells in which interference coupling levels may still
be relatively high, and interference mitigation techniques may be
implemented for such neighboring cells, such as DL and/or UL power
control methods. In some embodiments, two thresholds may be used
for cell cluster formation. In such embodiments, cells with a
relatively high level of coupling loss, above a first threshold,
are added to a same cluster. Such cells may reduce interference
through, for example, coordination of TDD UL-DL configurations. In
the example of FIG. 4, cell clusters 405-a, 405-b, and 405-c have
eNBs 105 that have interference coupling levels above the first
threshold. Cells with a moderate level of interference coupling,
such as a level of interference coupling above a second threshold
but below the first threshold, are added to a virtual logical cell
cluster 420-a, 420-b. According to some embodiments, cells in a
virtual logical cell cluster may have different transmit
directions, and employ one or more interference mitigation
techniques. In the example of FIG. 4, eNBs 105-f and 105-h belong
to virtual logical cell cluster 420-a, and eNBs 105-h and 105-i
belong to virtual logical cell cluster 420-b. Finally, cells with
relatively low level of interference coupling, e.g. interference
coupling less than the second threshold, may have different TX
direction without any interference mitigation applied to the
transmissions.
[0061] According to some embodiments, cell clusters may be formed
or re-formed based on conditions experienced by eNBs 105. An eNB
105 may belong to one physical cell cluster 405 and/or multiple
virtual logical cell clusters 420, based on eNB-eNB coupling loss.
As noted above, cells in one physical cell cluster 405 may
coordinate transmit directions based on aggregated traffic within
the cell cluster 405. The eNBs 105 in a same virtual logical cell
cluster 420 may have different transmit directions based on traffic
needs of the cell, but may apply scheduling-dependent IM schemes
(SDIM), such as DL and/or UL power control for example, to mitigate
eNB-to-eNB interference. In some embodiments a fixed delta, such as
a difference between the first and second thresholds for assigning
cells to clusters or virtual logical cell clusters, may be used as
a reference for interference mitigation. For example, with
reference to virtual logical cell cluster 420-a of FIG. 5, transmit
power of eNB 105-h may be reduced by "B-A" dBm to avoid strong
interference to eNB 105-i when eNB 105-i is configured for an
uplink transmission, so that interference from eNB 105-h to eNB
105-i is compatible to that from eNB 105-g, for example. In some
embodiments, TDD UL-DL configurations of neighbor cells in the same
cell clusters 405 and virtual logical cell clusters 420, may be
exchanged through control-plane messaging among eNBs, such as via
the S1 and/or X2 interfaces, for example.
[0062] The addition of one or more eNBs 105 to a cell cluster 405
and/or virtual logical cell cluster 420 may be performed in a
centralized manner by a network entity (e.g., a master eNB or an
entity on the core network), or in a distributed manner by
different eNBs 105. For centralized implementations, procedures and
X2 signaling may be provided to enable an eNB 105 to request a
change of TDD UL-DL configuration due to a change in UL-DL traffic
ratio, and to enable the master eNB (or other entity) to instruct
other eNBs 105 within the cell cluster 405 which UL-DL
configuration to use. The master eNB or other entity may also
inform other eNBs 105 in the same virtual logical cell clusters 420
about the selected TDD UL-DL configuration of other cells in the
virtual logical cell cluster 420, to enable SDIM for example. In
some cases, each eNB 105 may signal to other eNBs 105 in one or
more virtual logical cell clusters 420 the current TDD UL-DL
configuration. In decentralized implementations, procedures and X2
signaling may be provided to enable an eNB 105 to inform other eNBs
within a cell cluster 405 about its traffic pattern and selected
UL-DL configuration, and also inform other eNBs 105 in the same
virtual logical cell cluster 420 about the selected TDD UL-DL
configuration, to enable SDIM, for example. Such implementations
may provide for interference control only between edge cells of
clusters, rather than between entire clusters, thus providing
relatively efficient use of interference mitigation techniques.
Furthermore, such implementations may provide efficient exchange of
configuration information between cells in same cell clusters and
the same virtual logical cell clusters, and may also provide
efficient SDIM with fixed delta interference margin.
[0063] With reference now to FIG. 5, another example of a dual
threshold interference management technique in a CCIM environment
500 is described. In this example, an eNB 105-k has predefined
coupling loss thresholds which may be used to assign neighboring
cells to the same cell cluster or to a virtual logical cell
cluster. In this example, eNB 105-k may implement different
interference mitigation schemes for a ring like region defined by
coupling levels 505 and 510. The eNB 105-k may compare the coupling
loss (or interference coupling level) and corresponding thresholds
for each neighboring cell. Different interference mitigation
schemes may be identified based on the comparison. For example, if
the coupling loss for a neighboring cell is greater than or equal
to coupling loss threshold A, identified as the area within the
ring defined by coupling level 505 in FIG. 5, the TDD UL-DL
configurations of the two cells are coordinated. If the coupling
loss for a neighboring cell is less than coupling loss threshold A,
but greater than or equal to coupling loss threshold B, identified
as the area bounded by coupling levels 505 and 510, the eNB 105-k
and neighboring eNB may have different transmit directions and use
interference mitigation techniques, such as SDIM schemes, to
mitigate interference. If the coupling loss between eNB 105-k and a
neighboring eNB is less than threshold B, identified as the area
outside the ring defined by coupling level 510, no interference
mitigation techniques are required to be implemented. While the
example of FIG. 5 is described with reference to coupling loss
thresholds, similar techniques may use an interference coupling
level between neighboring eNBs that is correlated to coupling loss.
For example, eNB 105-k may identify a first interference coupling
threshold above which eNB 105-k and a neighboring eNB may be
assigned to a same cell cluster.
[0064] Similarly, eNB 105-k may identify a range of interference
coupling levels between a second interference coupling threshold
and the first interference coupling threshold for assigning the eNB
105-k and the neighboring eNB to a virtual logical cell cluster for
interference mitigation. Periodically, eNB 105-k may determine
whether the neighboring eNB is to be part of a same cell cluster or
a virtual logical cell cluster based on a level of interference
coupling between eNB 105-k and the neighboring eNB.
[0065] Thus, in order to provide reconfiguration and dynamic
resource allocation in eIMTA systems, various aspects of the
present disclosure provide for cell clustering based on
interference coupling levels. FIG. 6 shows a block diagram of a
wireless communications system 600 that may provide for
reconfiguration of TDD UL-DL configuration based on cell clustering
such as described above. This wireless communications system 600
may be an example of aspects of the system 100 depicted in FIG. 1,
CCIM environment 300 of FIG. 3, CCIM environment 400 of FIG. 4, or
CCIM environment 500 of FIG. 5. System 600 may include a base
station 105-l, which may be an example of a base station of FIG. 1
or 3-5. The base station 105-l may include antenna(s) 645, a
transceiver module 650, memory 670, and a processor module 660,
which each may be in communication, directly or indirectly, with
each other (e.g., over one or more buses 680). The transceiver
module 650 may be configured to communicate bi-directionally, via
the antenna(s) 645, with UEs 115-a, 115-b. The transceiver module
650 (and/or other components of the base station 105-f) may also be
configured to communicate bi-directionally with one or more
networks. In some cases, the base station 105-l may communicate
with the core network 130-a through network communications module
665. Base station 105-f may be an example of an eNodeB base
station, a Home eNodeB base station, a NodeB base station, and/or a
Home NodeB base station.
[0066] Base station 105-f may also communicate with other base
stations 105, such as base station 105-m and base station 105-n. In
some cases, base station 105-f may communicate with other base
stations such as 105-m and/or 105-n utilizing base station
communication module 630. In some embodiments, base station
communication module 630 may provide an X2 interface within an LTE
wireless communication technology to provide communication between
some of the base stations 105. In some embodiments, base station
105-l may communicate with other base stations through core network
130-a.
[0067] The memory 670 may include random access memory (RAM) and
read-only memory (ROM). The memory 670 may also store
computer-readable, computer-executable software code 675 containing
instructions that are configured to, when executed, cause the
processor module 660 to perform various functions described herein
(e.g., TDD UL-DL reconfiguration, cell clustering determination,
interference mitigation, etc.). Alternatively, the software code
675 may not be directly executable by the processor module 660 but
be configured to cause the processor, e.g., when compiled and
executed, to perform functions described herein.
[0068] The processor module 660 may include an intelligent hardware
device, e.g., a central processing unit (CPU), a microcontroller,
an application-specific integrated circuit (ASIC), etc. The
transceiver module(s) 650 may include a modem configured to
modulate the packets and provide the modulated packets to the
antenna(s) 645 for transmission, and to demodulate packets received
from the antenna(s) 645. While some examples of the base station
105-l may include a single antenna 645, the base station 105-l may
include multiple antennas 645 for multiple links which may support
carrier aggregation. For example, one or more links may be used to
support macro communications with UEs 115-a, 115-b.
[0069] According to the architecture of FIG. 6, the base station
105-l may further include a communications management module 640.
The communications management module 640 may manage communications
with other base stations 105. By way of example, the communications
management module 640 may be a component of the base station 105-l
in communication with some or all of the other components of the
base station 105-l via a bus 680. Alternatively, functionality of
the communications management module 640 may be implemented as a
component of the transceiver module 650, as a computer program
product, and/or as one or more controller elements of the processor
module 660.
[0070] In some embodiments, the transceiver module 650 in
conjunction with antenna(s) 645, along with other possible
components of base station 105-l, may determine TDD UL-DL
configurations for various UEs communicating with the base station
105-l. In some embodiments, base station 105-l includes a TDD UL-DL
configuration selection module 605 that determines a TDD UL-DL
configuration for UEs 115-a, 115-b. At some point, traffic patterns
may change such than an initial TDD UL-DL configuration is not
optimal for one or more UEs 115-a and 115-b. For example, TDD UL-DL
configuration selection module 605 may determine that the UL-DL
configuration for UE 115-b is to be reconfigured to a different
UL-DL configuration. Reconfiguration information may be provided to
UL-DL reconfiguration transmission module 610, which may transmit
TDD UL-DL reconfiguration messages, in conjunction with transceiver
module(s) 650, to the UE 115-b. Base station 105-l, in the example
of FIG. 6, also includes interference mitigation module 615.
Interference mitigation module 615 may include clustering
determination module 620 and interference management module 625.
Clustering determination module 620 may determine cell clusters
and/or virtual logical cell clusters to which the base station
105-l, and/or one or more other base stations, are to belong.
Clustering determination module 620 may make such determinations
using, for example, dual thresholds for interference coupling
levels between base station 105-l and neighboring cells, such as
described above. Interference management module 625 may provide
interference management for base station 105-l, such as through
coordination of TDD UL-DL configurations between cells that are in
the same cell cluster, and interference mitigation such as SDIM for
cells that are in one or more virtual logical cell clusters with
base station 105-l, such as described above.
[0071] According to some examples, a base station may determine the
TDD UL-DL configuration and reconfiguration associated with a UE,
and also transmit information related to configuration and
reconfiguration to be used for interference management by other
base stations. With reference now to FIG. 7, an example wireless
communication system 700 that performs TDD UL/DL reconfiguration
and related interference management is depicted. System 700
includes a UE 115-c that may communicate with base station 105-o to
receive access to one or more wireless networks, and may be an
example of aspects of the system 100 of FIG. 1, CCIM environment
300 of FIG. 3, CCIM environment 400 of FIG. 4, CCIM environment 500
of FIG. 5, or system 600 of FIG. 6. UE 115-c may be an example of a
user equipment 115 of FIG. 1, 3-4, or 6. UE 115-c, includes one or
more antenna(s) 705 communicatively coupled to receiver module(s)
710 and transmitter module(s) 715, which are in turn
communicatively coupled to a control module 720. Control module 720
includes one or more processor module(s) 725, a memory 730 that may
include computer-executable software code 735, and a TDD
reconfiguration module 740. The software code 735 may be for
execution by processor module 725 and/or TDD reconfiguration module
740.
[0072] The processor module(s) 725 may include an intelligent
hardware device, e.g., a central processing unit (CPU), a
microcontroller, an application specific integrated circuit (ASIC),
etc. The memory 730 may include random access memory (RAM) and
read-only memory (ROM). The memory 730 may store computer-readable,
computer-executable software code 735 containing instructions that
are configured to, when executed (or when compiled and executed),
cause the processor module 725 and/or TDD reconfiguration module
740 to perform various functions described herein. The TDD
reconfiguration module 740 may be implemented as a part of the
processor module(s) 725, or may be implemented using one or more
separate CPUs or ASICs, for example. The transmitter module(s) 715
may transmit to base station 105-o (and/or other base stations) to
establish communications with one or more wireless communications
networks (e.g., E-UTRAN, UTRAN, etc.), as described above. The TDD
reconfiguration module 740 may be configured to receive TDD
reconfiguration messages from base station 105-o change a TDD UL-DL
configuration, and send and receive transmissions according to one
or more interference management techniques that may be employed by
base station 105-o. The receiver module(s) 710 may receive downlink
transmissions from base station 105-g (and/or other base stations),
such as described above. Downlink transmissions are received and
processed at the user equipment 115-c. The components of UE 115-c
may, individually or collectively, be implemented with one or more
Application Specific Integrated Circuits (ASICs) adapted to perform
some or all of the applicable functions in hardware. Each of the
noted modules may be a means for performing one or more functions
related to operation of the UE 115-c.
[0073] FIG. 8 is a block diagram of a system 800 including a base
station 105-p and a UE 115-d. This system 800 may be an example of
the system 100 of FIG. 1, CCIM environment 300 of FIG. 3, CCIM
environment 400 of FIG. 4, system 600 of FIG. 6, or system 700 of
FIG. 7. The base station 105-p may be equipped with antennas 834-a
through 834-x, and the UE 115-d may be equipped with antennas 852-a
through 852-n. At the base station 105-p, a transmit processor 820
may receive data from a data source.
[0074] The transmit processor 820 may process the data. The
transmit processor 820 may also generate reference symbols, and a
cell-specific reference signal. A transmit (TX) MIMO processor 830
may perform spatial processing (e.g., precoding) on data symbols,
control symbols, and/or reference symbols, if applicable, and may
provide output symbol streams to the transmit modulators 832-a
through 832-x. Each modulator 832 may process a respective output
symbol stream (e.g., for OFDM, etc.) to obtain an output sample
stream. Each modulator 832 may further process (e.g., convert to
analog, amplify, filter, and upconvert) the output sample stream to
obtain a downlink (DL) signal. In one example, DL signals from
modulators 832-a through 832-x may be transmitted via the antennas
834-a through 834-x, respectively according to a particular TDD
Uplink/Downlink configuration.
[0075] At the UE 115-d, the UE antennas 852-a through 852-n may
receive the DL signals according to the particular TDD
Uplink/Downlink configuration from the base station 105-p and may
provide the received signals to the demodulators 854-a through
854-n, respectively. Each demodulator 854 may condition (e.g.,
filter, amplify, downconvert, and digitize) a respective received
signal to obtain input samples. Each demodulator 854 may further
process the input samples (e.g., for OFDM, etc.) to obtain received
symbols. A MIMO detector 856 may obtain received symbols from all
the demodulators 854-a through 854-n, perform MIMO detection on the
received symbols if applicable, and provide detected symbols. A
receive processor 858 may process (e.g., demodulate, deinterleave,
and decode) the detected symbols, providing decoded data for the UE
115-d to a data output, and provide decoded control information to
a processor 880, or memory 882. The processor 880 may be coupled
with a TDD reconfiguration module 740-a that may reconfigure the
TDD UL-DL configuration of UE 115-d according to a received
reconfiguration message, such as described above. The processor 880
may perform frame formatting according to a current TDD UL/DL
configuration, and may thus flexibly configure the TDD UL/DL frame
structure based on the current UL/DL configuration of the base
station 105-p.
[0076] On the uplink (UL), at the UE 115-d, a transmit processor
864 may receive and process data from a data source. The transmit
processor 864 may also generate reference symbols for a reference
signal. The symbols from the transmit processor 864 may be precoded
by a transmit MIMO processor 866 if applicable, further processed
by the demodulators 854-a through 854-n (e.g., for SC-FDMA, etc.),
and be transmitted to the base station 105-p in accordance with the
transmission parameters received from the base station 105-p. At
the base station 105-p, the UL signals from the UE 115-d may be
received by the antennas 834, processed by the modulators 832,
detected by a MIMO detector 836 if applicable, and further
processed by a receive processor 838. The receive processor 838 may
provide decoded data to a data output and to the processor 840. A
memory 842 may be coupled with the processor 840. The processor 840
may perform frame formatting according to a current TDD UL/DL
configuration. An interference mitigation module 615-a may, in some
embodiments, determine clustering information and related
interference mitigation, such as described above. Similarly as
discussed above, system 800 may support operation on multiple
component carriers, each of which include waveform signals of
different frequencies that are transmitted between base station
105-p and UE 115-d. Multiple component carriers may carry uplink
and downlink transmissions between UE 115-d and base station 105-p,
and base station 105-p may support operation on multiple component
carriers that may each have different TDD configurations. The
components of the UE 115-d may, individually or collectively, be
implemented with one or more Application Specific Integrated
Circuits (ASICs) adapted to perform some or all of the applicable
functions in hardware. Each of the noted modules may be a means for
performing one or more functions related to operation of the system
800. Similarly, the components of the base station 105-p may,
individually or collectively, be implemented with one or more
Application Specific Integrated Circuits (ASICs) adapted to perform
some or all of the applicable functions in hardware. Each of the
noted components may be a means for performing one or more
functions related to operation of the system 800.
[0077] FIG. 9 illustrates a method 900 that may be carried out by
one or more components of wireless communications system according
to various embodiments. The method 900 may, for example, be
performed by an eNB of FIG. 1, or 3-8, an entity located on a core
network of FIG. 1 or 6, or using any combination of the devices
described for these figures. Initially, at block 905, a plurality
of neighboring cells are identified for a first cell. At block 910,
a level of interference coupling between the first cell and each
identified neighboring cell is determined. A first neighboring cell
is added to a cell cluster of the first cell when the level of
interference coupling of the first neighboring cell exceeds a first
threshold, according to block 915. At block 920, a second
neighboring cell is added to a virtual logical cell cluster when
the level of interference coupling of the second neighboring cell
is between a second threshold and the first threshold, the second
threshold being less than the first threshold. Finally,
interference mitigation is performed between the first cell and one
or more cells in the virtual logical cell cluster, as indicated at
block 925. In such a manner, cell clusters and virtual logical cell
clusters may be identified to provide enhanced interference
mitigation.
[0078] FIG. 10 illustrates another method 1000 that that may be
carried out by one or more components of wireless communications
system according to various embodiments. The method 1000 may, for
example, be performed by an eNB of FIG. 1, or 3-8, an entity
located on a core network of FIG. 1 or 6, or using any combination
of the devices described for these figures. Initially, at block
1005, a plurality of neighboring cells are identified for a first
cell. At block 1010, a level of interference coupling between the
first cell and each identified neighboring cell is determined. A
first neighboring cell is added to a cell cluster of the first cell
when the level of interference coupling of the first neighboring
cell exceeds a first threshold, according to block 1015. At block
1020, a second neighboring cell is added to a virtual logical cell
cluster when the level of interference coupling of the second
neighboring cell is between a second threshold and the first
threshold, the second threshold being less than the first
threshold. At block 1025, TDD uplink-downlink (UL-DL) transmissions
are coordinated between the first cell and one or more cells in the
cell cluster, thereby providing interference mitigation for cells
of the cell cluster. At block 1030, one or more SDIM schemes are
applied between the first cell and one or more cells in the virtual
logical cell cluster.
[0079] FIG. 11 illustrates a method 1100 that that may be carried
out by one or more components of wireless communications system
according to various embodiments. The method 1100 may, for example,
be performed by an eNB of FIG. 1, or 3-8, an entity located on a
core network of FIG. 1 or 6, or using any combination of the
devices described for these figures. Initially, at block 1105, a
plurality of neighboring cells are identified for a first cell. At
block 1110, a level of interference coupling between the first cell
and each identified neighboring cell is determined. A first
neighboring cell is added to a cell cluster of the first cell when
the level of interference coupling of the first neighboring cell
exceeds a first threshold, according to block 1115. At block 1120,
a second neighboring cell is added to a virtual logical cell
cluster when the level of interference coupling of the second
neighboring cell is between a second threshold and the first
threshold, the second threshold being less than the first
threshold. At block 1125, interference mitigation is performed
between the cell and one or more cells in the virtual logic cell
cluster. At block 1130, a TDD UL-DL configuration of one or more
cells in the cell cluster is changed. Such a change may result, for
example, from a reconfiguration of the TDD UL-DL configuration for
one or more of the cells in the cell cluster. Finally, at block
1135, an updated TDD UL-DL configuration is transmitted to one or
more cells in the virtual logic cell cluster. Such transmission may
be transmitted via the X1 interface, for example.
[0080] FIG. 12 illustrates another method 1200 that that may be
carried out by one or more components of wireless communications
system according to various embodiments. The method 1200 may, for
example, be performed by an eNB of FIG. 1, or 3-8, an entity
located on a core network of FIG. 1 or 6, or using any combination
of the devices described for these figures. Initially, at block
1205, a first interference coupling threshold is identified, above
which a first cell and a neighboring cell are assigned to a same
cell cluster. At block 1210, a range of interference coupling
levels is identified between a second interference coupling
threshold and the first interference coupling threshold for
assigning the first cell and the neighboring cell to a virtual
logical cell cluster for interference mitigation. Finally, at block
1215, it is determined whether the first cell and the neighboring
cell are to be part of a same cell cluster or a virtual logical
cell cluster based on a level of interference coupling between the
first cell and the neighboring cell. Cells within a same cell
cluster may coordinate TDD UL-DL transmissions, for example, while
interference mitigation for cells in the virtual logical cell
cluster may include applying one or more scheduling-dependent
interference management (SDIM) schemes.
[0081] The detailed description set forth above in connection with
the appended drawings describes exemplary embodiments and does not
represent the only embodiments that may be implemented or that are
within the scope of the claims. The term "exemplary" used
throughout this description means "serving as an example, instance,
or illustration," and not "preferred" or "advantageous over other
embodiments." The detailed description includes specific details
for the purpose of providing an understanding of the described
techniques. These techniques, however, may be practiced without
these specific details. In some instances, well-known structures
and devices are shown in block diagram form in order to avoid
obscuring the concepts of the described embodiments.
[0082] Information and signals may be represented using any of a
variety of different technologies and techniques. For example,
data, instructions, commands, information, signals, bits, symbols,
and chips that may be referenced throughout the above description
may be represented by voltages, currents, electromagnetic waves,
magnetic fields or particles, optical fields or particles, or any
combination thereof.
[0083] The various illustrative blocks and modules described in
connection with the disclosure herein may be implemented or
performed with a general-purpose processor, a digital signal
processor (DSP), an application specific integrated circuit (ASIC),
a field programmable gate array (FPGA) or other programmable logic
device, discrete gate or transistor logic, discrete hardware
components, or any combination thereof designed to perform the
functions described herein. A general-purpose processor may be a
microprocessor, but in the alternative, the processor may be any
conventional processor, controller, microcontroller, or state
machine. A processor may also be implemented as a combination of
computing devices, e.g., a combination of a DSP and a
microprocessor, multiple microprocessors, one or more
microprocessors in conjunction with a DSP core, or any other such
configuration.
[0084] The functions described herein may be implemented in
hardware, software executed by a processor, firmware, or any
combination thereof. If implemented in software executed by a
processor, the functions may be stored on or transmitted over as
one or more instructions or code on a computer-readable medium.
Other examples and implementations are within the scope and spirit
of the disclosure and appended claims. For example, due to the
nature of software, functions described above can be implemented
using software executed by a processor, hardware, firmware,
hardwiring, or combinations of any of these. Features implementing
functions may also be physically located at various positions,
including being distributed such that portions of functions are
implemented at different physical locations. Also, as used herein,
including in the claims, "or" as used in a list of items prefaced
by "at least one of" indicates a disjunctive list such that, for
example, a list of "at least one of A, B, or C" means A or B or C
or AB or AC or BC or ABC (i.e., A and B and C).
[0085] Computer-readable media includes both computer storage media
and communication media including any medium that facilitates
transfer of a computer program from one place to another. A storage
medium may be any available medium that can be accessed by a
general purpose or special purpose computer. By way of example, and
not limitation, computer-readable media can comprise RAM, ROM,
EEPROM, CD-ROM or other optical disk storage, magnetic disk storage
or other magnetic storage devices, or any other medium that can be
used to carry or store desired program code means in the form of
instructions or data structures and that can be accessed by a
general-purpose or special-purpose computer, or a general-purpose
or special-purpose processor. Also, any connection is properly
termed a computer-readable medium. For example, if the software is
transmitted from a website, server, or other remote source using a
coaxial cable, fiber optic cable, twisted pair, digital subscriber
line (DSL), or wireless technologies such as infrared, radio, and
microwave, then the coaxial cable, fiber optic cable, twisted pair,
DSL, or wireless technologies such as infrared, radio, and
microwave are included in the definition of medium. Disk and disc,
as used herein, include compact disc (CD), laser disc, optical
disc, digital versatile disc (DVD), floppy disk and blu-ray disc
where disks usually reproduce data magnetically, while discs
reproduce data optically with lasers. Combinations of the above are
also included within the scope of computer-readable media.
[0086] The previous description of the disclosure is provided to
enable a person skilled in the art to make or use the disclosure.
Various modifications to the disclosure will be readily apparent to
those skilled in the art, and the generic principles defined herein
may be applied to other variations without departing from the
spirit or scope of the disclosure. Throughout this disclosure the
term "example" or "exemplary" indicates an example or instance and
does not imply or require any preference for the noted example.
Thus, the disclosure is not to be limited to the examples and
designs described herein but is to be accorded the widest scope
consistent with the principles and novel features disclosed
herein.
* * * * *